Build a RedeemerTagger for the opt-in redeemer labels streamed by --streaming-json (the redeemerKind / redeemerPayload fields on each script input).

The RedeemerTagger is a method on the TestingInterface class with a no-op default, so you only need one of the helpers below when you actually want human-readable redeemer labels in the stream. The tagger is handed the redeemer as Plutus Data, so it behaves the same for Plutus and Aiken validators provided the Haskell side has a FromData instance for the redeemer type.

• autoRedeemerTag decodes the redeemer and labels it with its show output. That is enough for plain enumerations such as Ping | Pong | Stop, where the constructor name is the label you want.
• labelRedeemer decodes the redeemer and runs your own function over it, so you control both the label and an optional JSON payload. Reach for it when show is not a clean label (for example a single-constructor record) or when you want the redeemer's fields attached as payload.

If neither fits, build a RedeemerTagger straight from any 'Data -> Maybe RedeemerTag' function; AikenBankSpec shows this by matching on Constr indices by hand.

The PingPongSpec is the simplest end-to-end example:

instance TestingInterface MyModel where
  redeemerTagger = autoRedeemerTag (Proxy @MyRedeemer)